6.4-stable review patch. If anyone has any objections, please let me know.
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From: Ryusuke Konishi konishi.ryusuke@gmail.com
commit f83913f8c5b882a312e72b7669762f8a5c9385e4 upstream.
A syzbot stress test reported that create_empty_buffers() called from nilfs_lookup_dirty_data_buffers() can cause a general protection fault.
Analysis using its reproducer revealed that the back reference "mapping" from a page/folio has been changed to NULL after dirty page/folio gang lookup in nilfs_lookup_dirty_data_buffers().
Fix this issue by excluding pages/folios from being collected if, after acquiring a lock on each page/folio, its back reference "mapping" differs from the pointer to the address space struct that held the page/folio.
Link: https://lkml.kernel.org/r/20230805132038.6435-1-konishi.ryusuke@gmail.com Signed-off-by: Ryusuke Konishi konishi.ryusuke@gmail.com Reported-by: syzbot+0ad741797f4565e7e2d2@syzkaller.appspotmail.com Closes: https://lkml.kernel.org/r/0000000000002930a705fc32b231@google.com Tested-by: Ryusuke Konishi konishi.ryusuke@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/nilfs2/segment.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/fs/nilfs2/segment.c +++ b/fs/nilfs2/segment.c @@ -725,6 +725,11 @@ static size_t nilfs_lookup_dirty_data_bu struct folio *folio = fbatch.folios[i];
folio_lock(folio); + if (unlikely(folio->mapping != mapping)) { + /* Exclude folios removed from the address space */ + folio_unlock(folio); + continue; + } head = folio_buffers(folio); if (!head) { create_empty_buffers(&folio->page, i_blocksize(inode), 0);